Exploring the Relationship Between Volumes, Crashes, and Speeds

1. Introduction

Exploring the Relationship Between Volumes, Crashes, and Speeds

1.1. Background

Using BikePed Portal data, this case study examines the relationships between bike and pedestrian volumes, surrounding vehicle speeds (RITIS), and bike/ped crashes occurred around permanent count locations. In crash analysis, the exposure effect to motorized vehicles is one of the most important crash risk factors. A typical way to measure the exposure effect is to count the volume of each mode. In addition, vehicle speed has a significant impact on the severity of the crash. Therefore, this case study studies whether the frequency of crashes is affected by volumes of pedestrians and cyclists and vehicle speed. The study sites are permanent count locations in the state of Oregon, Washington, D.C., and Arlington County, Virginia. The study uses the most recent data available (2018-2023).

1.2. Unit for Analysis

The spatial unit is the space within a half-mile straight-line buffer from the permanent count location. This was set because it is difficult to measure the traffic volume by mode at all points where a collision between modes can occur. Given that traffic volume affects the frequency of crashes, it was assumed that the number of bicycles or pedestrians measured within a half-mile would represent the traffic volume accounting for those crashes.

2. Data

2.1. Basic Information of Data

Location: Oregon, Virginia, Washington D.C.

Analysis Year: 2018-2023

Used Data: bike & pedestrian count (volume), crash , Census Block group, speed

Data Source/Year

Data Source Year
Bike/Pedestrian Counts BikePed Portal 2018–2023
Bike/Pedestrian–involved Crash ODOT*, VDOT, DDOT 2018–2023
Land Use (Zoning) Type–DC Open Data DC 2016
Land Use (Zoning) Type–OR Oregon GEOHub Data 2023
Land Use (Zoning) Type–VA Arlington Virginia ACMaps 2021
Census Block Group Population & Land Area–DC Open Data DC 2020
Census Block Group Population & Land Area–OR Oregon GEOHub Data 2020
Census Block Group Population & Land Area–VA Virginia Open Data Portal 2020
Speed–DC, OR, VA RITIS 2018–2023

*Note that ODOT provides crash data with location information through 2022. Since location information is a very important feature in this study, only cases where the location of each crash case was provided were analyzed.

2.2. Characteristics of Bike/Ped Crashes & Volume

2.2.1. Population Density (2020) nearby Bike/Ped Volume Data Count Location

Population Density is the average value within half-mile straight buffer area from the Bike/Ped Volume Counting Spot using census block group population number and area (square-mile)

Following characteristics of pedestrian and bike volume and crash counts are accumulated of each permanent count location

2.2.2. Accumulated Bike/Ped Volume by Characteristics of Permanent Count Location

No count numbers for the “Bridge” and “Intersection” doesn’t mean that there are no cyclists on the bridges or intersections. It means that the number of cyclists was not collected on the bridges and intersections.

No count numbers for the “Bikelane”, Bridge” and “Intersection” doesn’t mean that there are no pedestrians on the bike lanes, bridges or intersections. It means that the number of pedestrians was not collected on the bike lanes, bridges and intersections.

2.2.3. Bike/Ped Crash by Characteristics of Data Collecting Locations

2.2.4. Vehicle Speed near the Permanent Counting Location

3. Bike/Ped Crash & Volume Trend by Year

3.1. Bike Crash/Volume Trend by Year

3.2. Pedstrian Crash/Volume Trend by Year

3.3. Vehicle Speed Trend by Year & State

4. Bike/Ped Crash & Volume Trend by Month

4.1. Bike Crash/Volume Trend by Month

4.2. Pedestrian Crash/Volume Trend by Month

4.3. Vehicle Speed Trend by Month

5. Relationship between Crash & Volume & Population by State

5.1. Population & Bike Crash/Volume by State

5.2. Population & Pedestrian Crash/Volume by State

6. Crash & Volume & Vehicle Speed

6.1. Bike Crashes near Permanent Count Locations

6.2. Pedestrian Crashes near Permanent Count Locations